HD 95881: A gas rich to gas poor transition disk?

TL;DR

This study investigates the transition of the circumstellar disk around HD 95881 from gas-rich to gas-poor, revealing a complex structure with a puffed-up inner rim and a flaring outer region, indicating an evolutionary phase.

Contribution

The paper provides detailed spatial mapping and modeling of the gas and dust distribution around HD 95881, demonstrating a transitional disk structure with both gas-rich and gas-poor features.

Findings

The disk has a thick inner rim and a flaring outer region.

The outer disk is relatively void of visible dust grains.

HD 95881 is in a transition phase from gas-rich to gas-poor disk.

Abstract

Context. Based on the far infrared excess the Herbig class of stars is divided into a group with flaring circumstellar disks (group I) and a group with flat circumstellar disks (group II). Dust sedimentation is generally proposed as an evolution mechanism to transform flaring disks into flat disks. Theory predicts that during this process the disks preserve their gas content, however observations of group II Herbig Ae stars demonstrate a lack of gas. Aims. We map the spatial distribution of the gas and dust around the group II Herbig Ae star HD 95881. Methods. We analyze optical photometry, Q-band imaging, infrared spectroscopy, and K and N-band interferometric spectroscopy. We use a Monte Carlo radiative transfer code to create a model for the density and temperature structure which quite accurately reproduces all the observables. Results. We derive a consistent picture in which the disk consists of a thick puffed up inner rim and an outer region which has a flaring gas surface and is relatively void of 'visible' dust grains. Conclusions. HD 95881 is in a transition phase from a gas rich flaring disk to a gas poor self-shadowed disk.